The role of fractional calculus in modeling biological phenomena: A review

The small airways are defined as those less than 2 mm in diameter. They are a major site of pathology in many lung diseases, not least chronic obstructive pulmonary disease (COPD) and asthma. The small airways are frequently involved early in the course of these diseases, with significant pathology demonstrable often before the onset of symptoms or changes in spirometry and imaging. Despite their importance, they have proven relatively difficult to study. This is in part due to their relative inaccessibility to biopsy and their small size which makes their imaging difficult. Traditional lung function tests may only become abnormal once there is a significant burden of disease within them. This has led to the term ‘the quiet zone’ of the lung. In recent years, more specialised tests have been developed which may detect these changes earlier, perhaps offering the possibility of earlier diagnosis and intervention. These tests are now moving from the realms of clinical research laboratories into routine clinical practice and are increasingly useful in the diagnosis and monitoring of respiratory diseases. This article gives an overview of small airways physiology and some of the routine and more advanced tests of airway function. Keywords: chronic obstructive pulmonary disease; asthma; lung function; small airways; impulse oscillometry; multiple breath nitrogen washout; imaging (Published: 17 October 2014) Citation: European Clinical Respiratory Journal 2014, 1 : 25898 - http://dx.doi.org/10.3402/ecrj.v1.25898

https://www.tandfonline.com/doi/pdf/10.3402/ecrj.v1.25898

Techniques of assessing small airways dysfunction

Detection of changes in respiratory mechanics due to increasing degrees of airway obstruction in asthma by the forced oscillation technique

Spirometry is considered the primary method to detect the air flow limitation associated with obstructive lung disease. However, air flow limitation is the end-result of many factors that contribute to obstructive lung disease. One of these factors is increased airway resistance. Airway resistance is traditionally measured by relating air flow and driving pressure using body plethysmography, thus deriving airway resistance (Raw), specific airway resistance (sRaw), and specific airway conductance (sGaw). Other methods to measure airway resistance include the forced oscillation technique (FOT), which allows calculation of respiratory system resistance (RRS) and reactance (XRS), and the interrupter technique, which allows calculation of interrupter resistance (Rint). An advantage of these other methods is that they may be easier to perform than spirometry, making them particularly suited to patients who cannot perform spirometry, such as young children, patients with neuromuscular disorders, or patients on mechanical ventilation. Since spirometry also requires a deep inhalation, which can alter airway resistance, these alternative methods may provide more sensitive measures of airway resistance. Furthermore, the FOT provides unique information about lung mechanics that is not available from analysis using spirometry, body plethysmography, or the interrupter technique. However, it is unclear whether any of these measures of airway resistance contribute clinically important information to the traditional measures derived from spirometry (FEV1, FVC, and FEV1/FVC). The purpose of this paper is to review the physiology and methodology of these measures of airway resistance, and then focus on their clinical utility in relation to each other and to spirometry.

http://rc.rcjournal.com/content/respcare/57/1/85.full.pdf

What does airway resistance tell us about lung function

Impulse oscillometry in COPD: Identification of measurements related to airway obstruction, airway conductance and lung volumes

Changes in respiratory mechanics with increasing degrees of airway obstruction in COPD : Detection by forced oscillation technique

Background: Recent studies suggested that the bronchodilator response depends on airway obstruction. The forced oscillation technique (FOT) may help improve our u

/pdf/respiratory-impedance-and-response-to-salbutamol-in-healthy-9aiw8fjqby.pdf

Respiratory impedance and response to salbutamol in healthy individuals and patients with COPD.

OBJETIVO: Atualmente existem importantes debates na literatura sobre a resposta broncodilatadora em pacientes com DPOC e se a variacao do VEF1 pode ser considerada uma indicacao completa de reversibilidade neste caso particular. O objetivo deste estudo foi investigar o efeito do salbutamol nas propriedades resistivas e elasticas do sistema respiratorio de portadores de DPOC. METODOS: Foram avaliados 70 individuos com DPOC, classificados atraves da espirometria em dois grupos: broncodilatador (BD)-negativo (n = 39); e BD-positivo (n = 31). Utilizou-se a tecnica de oscilacoes forcadas (TOF) para avaliar os seguintes parâmetros: a resistencia no intercepto (R0), associada a resistencia total do sistema respiratorio; a resistencia media (Rm), relacionada a resistencia de vias aereas centrais; e a complacencia dinâmica (Cdyn); assim como o coeficiente angular da resistencia (S) e a reatância media (Xm), relacionados com a homogeneidade do sistema respiratorio. RESULTADOS: O uso do salbutamol resultou em reducoes significativas de R0 (p < 0,00002) e Rm (p < 0,0002). Foram tambem observadas elevacoes significativas em S (p < 0,0001), Cdyn (p < 0,0001) e Xm (p < 0,00004). Estas alteracoes ocorreram tanto nos dois grupos, tendo sido observadas maiores modificacoes nos parâmetros da TOF do que nos parâmetros da espirometria. CONCLUSOES: O uso de salbutamol melhorou o comportamento dos componentes resistivos e reativos do sistema respiratorio dos pacientes com DPOC estudados. Estas mudancas ocorreram independentemente da classificacao do exame empregando o VEF1, o que indica que a utilizacao deste parâmetro isoladamente pode nao ser suficiente para identificar completamente os efeitos fisiologicos envolvidos.

/pdf/bronchodilation-in-copd-beyond-fev1-the-effect-of-albuterol-4nxptotwlm.pdf

Ana Maria Gonçalves Tavares Di Mango

Papers

Changes in respiratory mechanics with increasing degrees of airway obstruction in COPD : Detection by forced oscillation technique

Respiratory impedance and response to salbutamol in healthy individuals and patients with COPD.

Bronchodilation in COPD: beyond FEV1-the effect of albuterol on resistive and reactive properties of the respiratory system